This invention relates to the ultrasonic, non-destructive testing of objects, and more particularly to apparatus employing digital signal processing and digital signal processing techniques for processing and displaying the results of such tests.
In copending U.S. Pat. No. 5,596,508, issued Jan. 21, 1997 entitled, "High Resolution Measurement of a Thickness Using Ultrasound," there is described an apparatus and a method for making highly accurate measurements of a material thickness using ultrasound. This non-destructive testing technique involves propagating an ultrasonic waveform having defined characteristics at an object or test specimen, and evaluating a return waveform to determine the attributes of the object or specimen to the desired degree of accuracy. In performing ultrasonic testing to measure material thickness, it is known to use sampling rates on the order of 100-500 MHz to obtain an accuracy level of 10*10.sup.-6 inches, and it is not unknown to use sampling rates in the gigahertz range. The electronic circuits typically used in processing test data to acquire these numbers for samples is emitter-coupled logic, or ECL. Further, it has heretofore been common to employ analog signal processing to generate a visual display of the return waveform which is then evaluated by an operator to determine whether or not the test specimen meets required specifications.
As an alternative to conventional ultrasonic testers, it is now possible to employ digital signal processing to evaluate the response waveforms and to perform pass/fail evaluations. A major advantage of using digital signal processing is that the sampling rate can now be on the order of 50 MHz, and still provide highly accurate measurement information to the user. Further, employing digital signal processing techniques enhances the accuracy of the results. In addition, digital signal processing techniques allow the signal processor to be interfaced with existing test equipment such as that described in the copending application, as well as other types of test equipment. Further, the signal processor apparatus can now provide a waveform display and data storage features which enable the user to immediately ascertain if a test specimen is acceptable as well as perform post-test analysis of the data obtained.